In-Depth Notes on Aquatic Biomes

Differences Between Marine and Freshwater Biomes

  • Chemical Variations:
    • Marine and freshwater biomes are distinguished by the level of dissolved salts.
    • Nutrient availability differs significantly between the two, influencing biotic communities.

Latitudinal Climate Variation

  • Impact on Aquatic Biomes:
    • Aquatic systems show less pronounced latitudinal variation compared to terrestrial ones.
    • Thermal properties of water lead to more stable conditions, affecting climate and biomes.

Zonation in Aquatic Biomes

  • Depth and Life:

    • Depth significantly influences environmental conditions in aquatic systems.
    • Photosynthesis is limited to a shallow zone (up to 200 meters) due to light penetration.
    • Below this zone, energy production relies on the benthic zone (the sea/lake bottom).

  • Benthic Zone:

    • Home to diverse organisms, including invertebrates, which contribute to nutrient cycling when organic matter settles.
    • Examples include the remains of dead organisms, which serve as nutrient sources.

Thermal Properties of Water

  • Seasonal Temperature Changes:
    • Water holds thermal energy effectively, leading to slow temperature changes.
    • Lakes may experience a temperature gradient, where surface water can freeze while deeper water remains at 4°C, limiting nutrient flow.

Types of Aquatic Ecosystems

  • Lakes:

    • Defined as enclosed bodies of water. Nutrient supply affects productivity (e.g., oligotrophic vs. eutrophic lakes).
    • Eutrophication: Excess nutrients lead to algal blooms and oxygen depletion.

  • Wetlands:

    • Areas characterized by water saturation and diverse flora and fauna.
    • Significant loss of wetlands in regions like New Zealand due to human activity.

  • Streams:

    • Have a gradient that affects water flow and biodiversity, particularly breeding grounds for many species.
    • Subject to pollution and degradation due to agricultural runoff and water extraction.

  • Estuaries:

    • Transition zones between freshwater and marine systems, exhibiting varied salinity and biological diversity.
    • Highly productive areas, often threatened by development and pollution.

Intertidal Zones

  • Defined as areas that experience regular submersion and exposure to tides.
  • Studied extensively for their unique adaptations to extreme conditions.

Marine Biodiversity

  • Coral Reefs:

    • Formed by the skeletons of cnidarians and harbor diverse ecosystems.
    • Require specific conditions for growth, often concentrated in warmer tropical waters.
    • Relationship with algae is crucial for nutrient production.

  • Oceanic Zone:

    • Comprises deeper waters beyond the continental shelf.
    • Biodiversity is influenced by factors like pressure, nutrient levels, and the presence of unique organisms adapted to extreme conditions.

Important Ecosystems and Human Impact

  • Problems: Overfishing, pollution, ocean acidification, and warming threaten marine biodiversity.
  • Conservation Needs: Emphasis on sustainable fishing practices and protection of critical habitats like coral reefs and estuaries.

Specific Ecosystem Examples

  • Hydrothermal Vents:
    • Unique ecosystems emerging around volcanic vents, supporting communities based on chemosynthesis rather than photosynthesis.
  • Dredging Practices:
    • Harmful effects on marine habitats when sediment is displaced, emphasizing the need for alternatives in fishing and habitat preservation.